Short-term responses of rehabilitating coastal dune forest ground vegetation to livestock grazing

We investigated the responses of the ground vegetation in a 17-year-old coa stal dune forest plant community to four levels of experimentally applied l ivestock grazing (three grazing levels and one ungrazed control) from May 1 994 to March 1996. The effects of grazing were apparently subordinate to si te-specific intrinsic vegetation change and there were some indications tha t rainfall interacted with grazing level. Grazing had some apparent but no significant effects on plant species composition, significantly affected pl ant species richness over time, and significantly increased the range of sp ecies richness and vegetation cover values as well as the relative abundanc e and numbers of plant species with erect growth forms. Vegetation cover ch anged significantly over time, independently of grazing. Our results point to two important, easily measured mechanisms for the conservation managemen t of coastal dune forests - the interaction of disturbance type with plant growth form and the increase of variation in community structural variables under disturbance. These mechanisms, although they potentially have wide a pplication and predictive power, have not been studied adequately.